/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
package org.apache.tomcat.websocket;

import javax.websocket.Extension;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.util.List;

/**
 * The internal representation of the transformation that a WebSocket extension
 * performs on a message.
 */
public interface Transformation {

	/**
	 * Sets the next transformation in the pipeline.
	 */
	void setNext(Transformation t);

	/**
	 * Validate that the RSV bit(s) required by this transformation are not
	 * being used by another extension. The implementation is expected to set
	 * any bits it requires before passing the set of in-use bits to the next
	 * transformation.
	 *
	 * @param i The RSV bits marked as in use so far as an int in the
	 *          range zero to seven with RSV1 as the MSB and RSV3 as the
	 *          LSB
	 * @return <code>true</code> if the combination of RSV bits used by the
	 * transformations in the pipeline do not conflict otherwise
	 * <code>false</code>
	 */
	boolean validateRsvBits(int i);

	/**
	 * Obtain the extension that describes the information to be returned to the
	 * client.
	 */
	Extension getExtensionResponse();

	/**
	 * Obtain more input data.
	 *
	 * @param opCode The opcode for the frame currently being processed
	 * @param fin    Is this the final frame in this WebSocket message?
	 * @param rsv    The reserved bits for the frame currently being
	 *               processed
	 * @param dest   The buffer in which the data is to be written
	 */
	TransformationResult getMoreData(byte opCode, boolean fin, int rsv, ByteBuffer dest) throws IOException;

	/**
	 * Validates the RSV and opcode combination (assumed to have been extracted
	 * from a WebSocket Frame) for this extension. The implementation is
	 * expected to unset any RSV bits it has validated before passing the
	 * remaining RSV bits to the next transformation in the pipeline.
	 *
	 * @param rsv    The RSV bits received as an int in the range zero to
	 *               seven with RSV1 as the MSB and RSV3 as the LSB
	 * @param opCode The opCode received
	 * @return <code>true</code> if the RSV is valid otherwise
	 * <code>false</code>
	 */
	boolean validateRsv(int rsv, byte opCode);

	/**
	 * Takes the provided list of messages, transforms them, passes the
	 * transformed list on to the next transformation (if any) and then returns
	 * the resulting list of message parts after all of the transformations have
	 * been applied.
	 *
	 * @param messageParts The list of messages to be transformed
	 * @return The list of messages after this any any subsequent
	 * transformations have been applied. The size of the returned list
	 * may be bigger or smaller than the size of the input list
	 */
	List<MessagePart> sendMessagePart(List<MessagePart> messageParts);

	/**
	 * Clean-up any resources that were used by the transformation.
	 */
	void close();
}
